High-speed communication systems are used ubiquitously in modern society. For example, nearly two-thirds of Americans own “smart phones”, and the “internet of things” promises to connect everyday objects, such as keys and kitchen appliances. In another example, modern vehicles (e.g., automobiles) use sophisticated, high-speed communication systems within the vehicle itself to control various functions, such as braking, crash prevention, and self-driving (e.g., automatic parking).
Computers and sensors communicate with each other over a network in the vehicle, for instance using transceivers. During initialization of a communication link (e.g., during startup of a device) a training signal may be sent from a transmitter of one device connected to the vehicle's network to a receiver of another device connected to the vehicle's network. The training signal can be used by the receiver to synchronize the receiver to the transmitter, such as by adjusting counters, a state machine, and/or a timing loop in the receiver. The receiver may also measure power of the received training signal and set one or more gains in the receiver processing chain based on the measured power, such as a gain prior to analog-to-digital conversion for proper loading of a digital-to-analog converter, and/or a gain in an equalizer module that sets a gain at the input of the equalizer.
Various sources introduce electromagnetic interferences into the vehicle environment, such as the vehicle's ignition system, cellular phones within the vehicle, atmospheric conditions (e.g., thunderstorms, solar rays, auroras, etc.) and cross talk from computers and sensors comprising the vehicle's communication system, e.g., computing devices connected to the vehicle's network. The interference can couple onto the vehicle's communication system and be of significant power relative to desired signals within the vehicle's communication system. When interference is present during initialization and/or startup, the interference can corrupt or prevent detection of a training signal, which can cause the receiver to improperly synchronize to the transmitting device, driving equalizer coefficients in the receiver to be adapted to an unusable setting. Furthermore, a request that another transmission of the training signal be sent may be required when interference prevents proper detection of the training signal. Moreover, power measurements at the receiver can be biased due to an interferer, causing improper setting of gains in the receiver processing chain, which can introduce non-linearities into the receiver path that degrade or prevent payload recovery.